Study Finds 80% of Infants With RSV Didn’t Have Underlying Conditions

A toddler is seen in a hospital bed.
RSV is a common virus that can cause more serious symptoms in children. Jill Lehmann Photography/Getty Images
  • RSV (respiratory syncytial virus) usually results in mild symptoms for most people.
  • But infants are at higher risk for complications due in part to their smaller airways.
  • A new study finds that most infants with the virus treated in the ICU didn’t have underlying conditions.

As summer winds down in the U.S., cold and flu season is just around the corner.

That means cases of RSV (respiratory syncytial virus)

is likely to increase in the coming months.

Now new research finds that most infants who were admitted last season to an intensive care unit for RSV were healthy before their infection, suggesting that preventative measures should be ramped up as we head into the next virus season.

RSV is a common lower respiratory virus that usually causes cold-like symptoms in healthy adults but is more likely to have serious symptoms in infants and older adults.

“RSV is a seasonal virus that is the leading cause of hospitalizations of infants in the U.S. That is a very powerful statement,” said Dr. William Schaffner, Professor, Preventative Medicine, Health Policy, Division of Infectious Diseases, Vanderbilt University School of Medicine. “It accounts for somewhere between 50,000 and 80,000 hospitalizations in children younger than five in the U.S. each year. About 20% of those require admission to the ICU.”

New study finds RSV can take a toll on healthy children

According to the Centers for Disease Control and Prevention, RSV is a lower respiratory virus that causes cold-like symptoms. Most people recover in one to two weeks, but in some cases, RSV can be serious, particularly in infants and older adults. 

In a new study published August 15 in JAMA Network Open, researchers looked at 600 infants who were hospitalized in the intensive care unit for RSV. They found over 80% of these children did not have any underlying health conditions before their illness.

Infants under 3 months of age, those born prematurely, and those who were publicly insured were at higher likelihood of needing to be intubated.

“RSV is a scary illness,” said Dr. Rebecca Fisk, a pediatrician at Northwell Lenox Hill Hospital. “RSV has a lot of morbidity in children under six months and particularly in children under three months because we know that even healthy children have very small airways. Smaller child, smaller airways. If you have even a little bit of inflammation from the virus or the mucus production in reaction to the virus, you’re narrowing the diameter of those airways significantly. It’s like taking a straw and making it a coffee stirrer.”

How is RSV transmitted? 

According to the CDC, RSV can spread when

  • An infected person coughs or sneezes
  • You get virus droplets from a cough or sneeze in your eyes, nose, or mouth
  • You have direct contact with the virus, like kissing the face of a child with RSV
  • You touch a surface that has the virus on it, like a doorknob, and then touch your face before washing your hands

Those who are infected with RSV are usually contagious for three to eight days and may become contagious a day or two before they start showing signs of illness. The CDC also says that infants, as well as people with weakened immune systems, may be able to spread the virus even after they stop showing symptoms. RSV can also survive for many hours on hard surfaces.

How to prevent RSV

The good news is that there are ways to prevent RSV, and the authors of this study are hoping to make preventive measures even more accessible.

The Food and Drug Administration (FDA) recently approved a monoclonal antibody that works to prevent RSV in children up to 24 months old. 

“We’re all very excited about having this monoclonal antibody for infants,” said Schaffner. “We anticipate preventing so much illness once we start using this medication for young infants on a routine basis. If we do this routinely, we can eliminate disparities in how this virus affects different populations.”

However, the antibody is only eligible for high-risk infants, but this new research suggests that since most infants from the study were not high-risk, RSV preventive interventions should target all infants to reduce the burden of severe RSV illness.

“[The antibody] is given to protect those children and infants that are at increased risk of severe RSV,” said Fisk. “To me, that means you give it to everyone.”

However, it should be noted that while the FDA has approved the monoclonal antibody and said it will be available “ahead of the 2023-2024 RSV season,” it has not provided specifics.

“We believe the season is October/November to April. They say one dose is recommended for an RSV season. What they didn’t tell us is when it is being released. It’s August, and if I as a pediatrician want to protect the babies I care for, I want to give it to them before RSV season. I want to give it to them by October, which means they have to start releasing it in the next four to six weeks. There are many unknowns here. The CDC and FDA approved it, but haven’t given guidelines.”

RSV vaccine for older adults

RSV is also not just a virus that can severely impact infants. It can also be severe for people over the age of 60. A new vaccine is currently available for adults over the age of 60, and experts are urging people to add the RSV vaccine to their annual inoculations.

“It’s a one-dose inoculation,” said Schaffner. “The CDC says you can get it along with one of the other vaccines [flu and COVID] if that’s your choice. This year we are all going to be learning about how to get the word out and how to organize ourselves so that patients have access to these three vaccines and we can provide them in the most efficient fashion. This is the first time out of the box that we have three vaccines that we’re talking about for the older population.”

As for the groups who are not eligible for the monoclonal antibody or the vaccine, the best way to prevent the spread of RSV is something we’ve been practicing for the past few years due to COVID — proper hygiene.

“RSV is by contact. It lives on clothing, toys, unwashed hands, and doorknobs,” said Fisk. “We don’t want to be neurotic, but we want to practice safe hygiene. We were all told to do this during COVID and we forgot about it because COVID numbers got better. We still need to do those precautions for RSV.”

Those precautions include wiping surfaces down with cleaning wipes, washing hands frequently, and staying away from others when we feel we have cold or flu-like symptoms.

“Try to avoid people who are coughing and sneezing. Let everyone know who visits that if they are going to visit, postpone if you have any respiratory symptoms,” said Schaffner. 


A new study finds that RSV can take a toll even on healthy children. It found that among 600 infants hospitalized in the intensive care unit for RSV, over 80% had no underlying health conditions prior to becoming ill.

Experts say there are steps parents can take to protect children including hygiene and a new monoclonal antibody treatment for children at risk. Older adults are eligible to get the RSV vaccine.

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